Japanese Laid Open Patent Publication No. 2010-105186 discloses an apparatus for successively making plastic bags of plastic film. The apparatus includes feeding means by which webs of plastic film are fed longitudinally thereof and intermittently for a length and along a path. The plastic bag has a size corresponding to the length. The apparatus further includes a plurality of movable units spaced from each other along the path. The movable units are supported for movement longitudinally of the webs of plastic film. The apparatus further includes a plurality of drive means each of which is mounted on each of the movable units for moving each of the movable units. The webs of plastic film are processed by at least some of the movable units to successively make the plastic bags. For example, the movable units comprise a longitudinal heater, a longitudinal cooler, a cross heater, a cross cooler and a cutter. The webs of plastic film are longitudinally heat sealed, cooled, cross heat sealed, cooled and cut by the longitudinal heater, the longitudinal cooler, the cross heater, the cross cooler and the cutter whenever being fed intermittently, to successively make the plastic bags.
In addition, the webs of plastic film are printed with a pattern over again. The movable units further comprise upstream and downstream optical sensors disposed upstream and downstream of the cross heater. The upstream or downstream optical sensor detects a position at which the webs of plastic film are printed, whenever the webs of plastic film are fed intermittently, to make the webs of plastic film stopped. The webs of plastic film are longitudinally heat sealed, cooled, cross heat sealed, cooled and cut after being stopped.
Furthermore, one of the movable units constitutes a point of reference. If the webs of plastic film suffer, extension or contraction when operating the apparatus, a control device controls the drive means to move the movable units for distances except the movable unit constituting the point of reference, after the webs of plastic film are stopped. The control device calculates the distances of moving the movable units in accordance with the extension or contraction of the webs of plastic film, before moving the movable units so that the distances can be proportional to intervals from the point of references to correspond to the extension or contraction of the webs of plastic film. It should therefore be understood that regardless of the extension or contraction, the webs of plastic film are longitudinally heat sealed, cooled, cross heat sealed, cooled and cut with accuracy.
By the way, the extension or contraction aside, the apparatus has problems about the positions of movable units. For example, the movable units are not always disposed in positions before operating the apparatus. An operator has therefore to move the movable units by hand for adjustment of position. In particular, the operator has often to move the cross heater and the cross cooler by hand for adjustment of position. In addition, it is conventional to change the size of plastic bag. In this case, the operator has to move the movable units by hand for adjustment of position so that the movable units can be spaced from each other for a distance corresponding to the size of plastic bag, taking labor and time.
It is therefore an object of the invention to provide an apparatus including a plurality of movable units to successively make plastic bags of plastic film, which can move the movable units for adjustment of position without difficulty before operating the apparatus.